Image production using photosensitive compositions of nitrone which is heat developed

ABSTRACT

The use of photosensitive nitrones in an image-formation system, if desired with auxiliary compounds for intensifying the photolytically formed image or for improving the fixing of the image, wherein the image is fixed by the use of heat.

United States Patent [191 Schlesinger 1451 Nov, 27, 1973 [5 IMAGE PRODUCTION USING 3,510,309 5/1970 Lev/18.. 96/90 R PHOTOSENSITIVE COMPOSITIONS OF 1582542 6/1971 9/1961 Karlson 96/60 NITRONE WHICH IS HEAT DEVELOPED Sheldon Irwin Schlesinger, l-lightstown, NJ.

Inventor:

Assignee: American Can Company,

Greenwich, Conn.

Filed: Nov. 27, 1970 Appl. No.: 93,414

Related US. Application Data- Continuation of Ser. No. 656,685, July 28, 1967, abandoned.

References Cited UNITED STATES PATENTS 12/1968 Sus et al. 96/88 X OTHER PUBLICATIONS J. Org. Chem, Vol. 23, April 1958, p. 651.

Primary Examiner--Norman G. Torchin Assistant Examiner-John L. Goodrow Attorney-Robert P. Auber, George P. Ziehmer, Leonard R. Kohan and Harries A. Mumma, Jr. 1

ABSTRACT The use of photosensitive nitrones in an imageformation system, if desired with auxiliary compounds 25 Claims, No Drawings IMAGE PRODUCTION USING PI-IOTOSENSITIVE COMPOSITIONS OF NITRONE WHICH IS HEAT DEVELOPED CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION This invention relates to new image-formation systems wherein the photosensitive material is a nitrone and in which the image may be fixed by the use of heat. It is'known to use nitrone in the formation of photo graphic images. In U. S. Pat. No. 2,426,894 nitrones are used in the production of images, but the method for fixing the image requires the use of aqueous washing procedures. The present system enables one to eliminate the necessity for aqueous washing and substitutes therefor heat treatment to fix the image.

In the process of the present invention, it is possible to use any photosensitive nitrone. A nitrone is an organic compound of the formula muc=Naa wherein R and R can be any alkyl or aryl group, R

can be hydrogen, an alkyl or aryl group. R R and R may be substituted. The nitrones wherein R and R are aryl groups are particularly valuable because these compounds have ultraviolet absorption maxima in the photographically useful region of the spectrum, above 300 mu. These may be represented by the formula RCI-I=N( O)R', where R and R are aryl groups, while certain other groups have been found likewise to be particularly beneficial as the R group in such nitrones. I

It is highly to be desired to find a new, efficient system for the direct reproduction of images. The nitrone system produces. a negative image of a positive. It is a reverse process, not a direct process, useful for example for the duplication of office correspondence, for the formation of microfilm, records and so on. There are many commercial duplicating systems which are now in satisfactory operation, but most exhibit some undesirable characteristics. The diazo system requires either the use of aqueous developers, gaseous ammonia or a dry reagent that yields an alkaline material upon heating, which makes for a complicated process. The systems based on the use of sensitive silver salts are proportionately expensive. If the reproduction system is to be used to form microfilm copies, it is necessary for the system to be capable of excellent definition. The systems of the present invention are capable of finer definition than conventional silver halide/gelatin systems.

SUMMARY OF THE INVENTION The novel process provided by the present invention comprises exposing, to an actinic-light image, a photo sensitive element or medium comprising a support having in operative association therewith a nitrone of the formula and fixing the exposed element by heat treatment. Preferred are photosensitive nitrones having the formula RCH=N( O)R', where R is selected from the group consisting of aryl including substituted phenyl aroyl, arylvinylene, and furyl groups and R is an aryl group including substituted phenyl, said substituted phenyl having one or two substituents selected from the group consisting of dimethylamino, hydroxy, methyl, and nitro. The exposure to actinic radiation should be carried out for a sufficient period of time to cause a chemical change in the nitrone in the exposed areas, converting the exposed nitrone to a durable product giving increased optical densities in the exposed image areas. The light-sensitive mediumfor forming the visible images advantageously carries, in addition to the nitrone compound, one or more auxiliary compounds for improving optical density in exposed image areas or for facilitating heat-fixing of unexposed or partially exposed image areas. It will appear that the terms photosensitive and light-sensitive as used herein refer to sensitivity to actinic radiation generally, the radiation preferably being ultraviolet light or visible light or both.

DETAILED DESCRIPTION The nitrones used in accordance with the present invention are generally of the formula wherein R or R may be alkyl or aryl or it may be substituted alkyl or aryl, while R may be a hydrogen, alkyl, aryl, substituted alkyl or aryl. The nitrones that are useful in this invention undergo a visible color change when exposed to actinic radiation or may produce a visible change by reaction of their photochemicalreaction products or intermediates with other added reagents. Preferred are the nitrones with an aryl, aroyl, arylvinylene, or furyl group on the alpha carbon and an aryl group on the nitrogen. Examples of these nitrones are:

alpha,N-diphenylnitrone alpha-( 3 ,4-dimethoxyphenyl )-N-phenylni trone alpha-(p-nitrophenyl )-N-phenylnitrone alpha-(p-methoxyphenyl)-N-phenylnitrone N-(p-dimethylaminophenyl)diphenylenemethylenenitrone (N-9-fluorenylidene-N',N'-dimethyl-p-phenylenediamine N-oxide) alpha-( 1 -naphthyl )-N-phenylnitrone alpha-(Z-hydroxyphenyl )-N-phenylnitrone alpha-phenyl-N-( l-naphthyl )nitrone alpha-phenyl-N-( 3-nitro-4-methylphenyl )nitrone alpha,alpha'-p-phenylenebis-N-phenylnitrone alpha,alpha-bis(diphenylnitrone) alpha 3 ,4-dihydroxyphenyl )-N-phenylnitrone alpha-(p-hydroxyphenyl )-N-phenylnitrone alpha-(4-hydroxy-3 -methoxyphenyl )-N- phenylnitrone alpha-phenyl-N-( m-nitrophenyl )nitrone alpha-(2,4-dinitrophenyl)-N-(dimethylaminophenyl)nitrone alpha-(p-dimethylaminophenyl)-N-phenylnitrone alphabenzoyl-N-phenylnitrone alpha-benzoyl-N-(p-dimethylaminophenyl)nitrone methoxy,

alpha-( 2-( l-naphthyl )vinylene )-N-phenylnitrone alpha-(trans-styryl)-N-phenylnitrone alpha-( 2-furfuryl )-N-phenylnitrone The present process uses a heat treatment to remove the unexposed photosensitive nitrones from the system. The heat-fixing may be accomplished with or without the addition of fixing agents, although the addition of fixing agents may increase the speed and efficiency of the fixing.

If the heat treatment is carried on adequately in the absence of an added fixing agent, the heating of the substrate bearing the nitrone results in the rearrangement or decomposition-of the nitrone to a practically colorless and non-photosensitive product. As illustrated in the examples hereinbelow, the heat-treating operation is carried out to maintain the nitrone at a temperature of at least 100C, and preferably approximating 135C, for an effective period which may be quite short, or which may be achieved by heating the medium for a quarter hour to two hours, thus converting the nitrone in unexposed image areas to a radiationstable product of low optical density without substantially decreasing the increased optical densities which have been obtained in the exposed image areas. For example, the rearrangement of alpha,N-diphenylnitrone to the benzanilide upon heat-fixing results in a colorless non-sensitive product according to the following equatron:

heat

The rearrangement advantageously may be catalyzed by the addition of such catalysts as phosphorus trichloride, phosphorus pentachloride, sulfur dioxide, thionyl chloride, acetic anhydride, maleic anhydride, and tricresyl phosphate. The catalyst may be added to the system by incorporation of a precursor in the photosensitive layer which would yield the agent upon application of heat.

The fixation of the image may be also improved by the addition of a reagent which reduces or deoxygenates the unexposed portions of the nitrone to an inactive form. Such reagents may be phosphines, sulfur dioxide, sulfur or precursors of these.

The efficiency of the thermal fixing may be greatly improved by incorporating into the photosensitive composition an ethylenically unsaturated compound such as acrylamide, N-methylolacrylamide, N,N'- methylenebisacrylamide, acrylonitrile, styrene, N-methylolmethacrylamide, substituted acrylamides (note the methyl-substituted compound methacrylamide, carrying also an additional N-substituent, just mentioned), N-vinylsuccinimide, N-vinylphthalimide, dimethyl fumarate and esters of acrylic and methacrylic acids, fumaronitrile, 3-sulfolene, and N- phenylacrylamide, as well as derivatives of acetylene such as phenylacetylene.

The efficiency of the thermal fixing in the presence of an unsaturated compound may be further enhanced by the presence of certain salts, such as lithium bromide, lithium p-toluenesulfonate or piperidinium p-toluenesulfonate.

The intensity of the nitrone image may be improved by the addition of organic amines and substituted phenols, e.g., alkoxyphenols, as intensifiers, for example, diphenylamine and p-phenylenediamine and their derivatives such as the N-aryl-substituted N,N'-diphenylp-phenylenediamine, indole, carbazole, benzimidazole, rhodanine, indole derivatives such as 3-indolylacetic acid, or p-methoxyphenol.

The rearrangement catalysts for facilitating heatfixing, the unsaturated heat-fixing reagents, and the diphenylamine and other image intensifiers will be seen to constitute together a group of auxiliary compounds which, cooperating with the photosensitivity and heatfixing properties of the nitrones alone, expedite or increase the permanent contrast obtainable between exposed and unexposed image areas in the visible image which is formed in the light-sensitive coated substrate or medium of the invention.

The nitrones of the present invention may be prepared by the condensation of N-monoarylhydroxylamines with aldehydes and ketones as in U. S. Pat. No. 2,426,894, or by the methodsoutlined by Hamer and Macaluso in Chemical Reviews, Vol. 64, August, 1964, pages 474492.

The nitrones may be utilized by impregnating them into at least a surface layer of a sheet of paper, cloth or other material. A supporting sheet carrying nitrone may be made by incorporating the nitrone into a film or layer coated on a plastic or metal substrate. Alternatively, a support may be made to carry the nitrone by incorporating the nitrone into a plastic film itself. The films may include cellulose acetate butyrate, cellulose acetate, lexan, microwaxes, polystyrene, polycarbonate, low-molecular-weight polyethylene, etc.

The following examples demonstrate the utility of the nitrones in a system where the image is heat-fixed. The densities of the images produced by the nitrones were read with a Welch Densichron Model 1 densitometer, using the reflection head for reading opaque images such as on paper and the transmission head for the transparent film images. The Welch Densichron conversion table was used to convert to percent reflection or transmission. The incident light colors referred to with respect to optical densities and percent reflections or transmissions were obtained using the following Kodak Wratten filters:

TRANSMISSION HEAD FILTERS Filter No. Transmission Peak, mu

92 Red 700 99 Green 550 98 Blue 430 REFLECTION HEAD FILTERS Filler No. 'lrunsmission Peak, mu

25A Red 700 588 Green 530 478 Blue 430 The degree of fixing of the photosensitive layer is derived from the precent difference between the reflection or transmission of the area of the test film exposed to actinic light before heating and the area exposed after heating.

The values quoted in the following tables are not the absolute differences between the percent reflections or the percent transmissions of each image but are the percent differences based upon the higher of the two values being compared.

In the reflection reading, the instrument was standardized with the white paper to be irradiated (which would later bear the image), and the standard value was subtracted from the actual reading to get the true optical density due to the photochemical reaction. With transmission readings, the same procedure was followed, using a clear unirradiated sample of the film as the standard. The relation between the optical density and the percent transmission or reflection is given by the equation D Log (Po/Pt).

D optical density I P incident light Pt transmitted or reflected light The percent reflection or transmission is given instead of the optical density because it is more meaningful for comparison of image intensities. For example, an optical density of 1 corresponds to a percent reflection of 10 percent, while an optical density of 2 corresponds to 1 percent reflection. Unless one is always aware that logarithmic values are dealt with in optical densities, it is not always readilyapparent that the latter value indicates 10 times the blackness of the former value. The use of percent reflection values makes this relationship more readily apparent. It should be remembered that the lowest percent reflection-transmission values represent the blackestor densest images. The Welch conversion table was used to derive percent reflection and transmissions from the observed optical density.

Example I A series of solutions is prepared. All solutions contain 0.200 N alpha, N-diphenylnitrone. To a 5 m1. aliquot of this solution, 0.154 gram of N,N'- methylenebisacrylamide is added. To a ml. aliquot of the solution, 0.196 gram of maleic anhydride is. added. To a 10 ml. aliquot of the solution, 1 drop of acetic anhydride is added. Two spots, individually designated spot A and spot B, are formed from each solution, including the two spots from the initial solution without a fixing agent, on samples of Whatman No. 2 filter paper. The spots are colorless upon drying. Spot A, of each, is exposed for 5 minutes at 12 cm distance from a BOO-watt Gates Raymaster ultraviolet light source. All the samples of filter paper are then heated at 135C. for 1 hour. Following the heating, spot B is exposed for 5 minutes in the same manner'as spot A. The following table shows the percent reflection data for each of the two spots and the percent difference due to fixing.

denser image than the spots which are heated before exposure. The percent reflections are consistently higher in the latter case of spot B.

Examples II XI The following series of experiments show the result of heat-fixing alpha,N-diphenylnitrone in cellulose acetate film. A film is formed on Mylar from a solution of 0.396 gram alpha,N-diphenylnitrone in 12.1 grams of 17.5 percent cellulose acetate in acetone. The dried film is divided into four areas, areas 1, 2, 3, and 4. Areas 3 and 4 are exposed for 15 minutes at 12 cm distance from a 300'watt Gates Raymaster ultraviolet source. The film sample is then heated at 135C for 1 hour. Areas 2 and 4 of the film samplesare then exposed to the same ultraviolet treatment as before. The optical densities to transmitted light are then read and converted to percent transmission. Area 1, which is not exposed, remains clear.

Solutions in the following series are prepared containing different additives and then are cast on a Mylar strip and treated in the same way as the film containing only the nitrone. In each case, area 1, the area which was not exposed to ultraviolet light, remains clear. A variety of ethylenically unsaturated compounds is used in Examples III-IX. As Example III, a solution of N-methylolmethacrylamide in the amount of 1.5 molar equivalents based on the nitrone is added to a base solution of the diphenylnitrone in cellulose acetate dissolved in acetone equivalent to 22 percent of the dry cellulose acetate weight. As Example IV, N- methylolacrylamide equivalent to 1.5 molar equivalents is added to the above base diphenylnitrone solu tion. One molar equivalent of N-vinylphthalimide is added to the base diphenylnitrone solution to give Example V. Dimethylfumarate is added to another quantity of base solution in the amount of 1 equivalent to produce Example VI. Fumaronitrile, as Example VII, is added to the base solution in the amount of 1 equivalent. As Example VIII, 3-sulfolene is added to the base solution in the amount of 1.1 equivalents. Styrene in Example IX is added in the amount of 1.5 equivalents. The acetylenically unsaturated compound phenylacetylene, as Example X, is added in the amount of 1.5 equivalents. Finally, as Example XI, one drop of tricresyl phosphate is added as a heat-fixing catalyst to PERCENT REFLECTIONS OF EXPOSED SAMPLE SPOTS ()N PAPER Percent reflections of difierent colored lights Spot exposed White Red Green Blue Added fixing agent:

None {ABel'ore heating... 47. 86 69. 18 51. 29 2!). 51 "'""""""'lBAfter heating-.- 66.07 83.18 67. 61 51. 29

Percent difierences 18. 21 14. 00 16.30 21.80

ABefore hearing--- 47.86 74.13 46. 77 26.92 --iB-A1ter hearing... 83.18 95. 89.13 66.07

Percent differences 42. 46 22.38 47. 53 66. 07

. I ABefore heating..- 35. 50 57. 50 35. 50 20.90

mhydnde "lBAfter heatin 66.07 85.10 66.07 46.80

Percent differences 47. 80 32. 40 46.30 55.40

- ABefore heating... 44. 70 69.20 44. 70 25.10 anhydnde "lBAfter heating. 63.10 81.30 63.10 46.80

Percent differences 29. 20 14. 29. 20 46. 30

As is evidenced in the above table, the spots (spot A) which are exposed and then fixed by heat produce a the stated base solution. The results from these different compositions are shown in the following table:

HEATING-FIXING TEST DATA IN CELLULOSE ACETATE FILM Percent transmission Added agent Area White Red Green Blue Percent difference 3'O .O 6.68 22.40 Iv --N-meIhyIOIIIIIYIamId@ --{i:::::::: 53:33 3%; 23:52 i811? Percent diflerenee 42.40 14.90 34.00 85.00

--N-VIIIYIPIIIIIIIIIIIII IQ -{li:::::::: 2H8 351i; 251?; 3333i Percent diiiercnce- 2 7f0 8.80 24.20 65.20 --I IImIII-vIIIIIImIIIII --{i:::::::: it??? 33:22 3333 It}? "i4 52.48 15. so 57.54 14.45

Percent diiiercnec ..l) 0 0 2 0 e0 49 s 0 IX SWIM --{Z:::::::: $313 23% Sit;

Percent difference 1i)0 10.90 X --IIIQIIYIIIIQIYIGIIQ --{i:::::::: 231% $3123 Z5122 iii? Percent dilierencclGJlO 10.00 Q XI --'IIIIIOSYIIIIIOSIIIIEII --{li:::::::: (132 315 221% 33:13

lercenl. difierencc 33. J0 14.90 32. 50 67.00

As shown in the above table, the results as evidenced 0.020 gram of lithium p-toluenesulfonate is added to from area 4 consistently show the lowest percent transyet another of the solutions. Finally, as Example XIV, mission and therefore area 4 contains the darkest im- 40 0.05 gram of piperidinium p-toluenesulfonate is added to the remaining prepared solution. Films are passed from these solutions on Mylar D producing a 7-mils wet thickness. The films are divided into sections as in Example II, etc., and treated as in connection therewith.

EXAMPLES XII XIV The effect of the addition of various salts on the image produced from a solution of nitrone containing However, it is found that only 15 minutes of heating at 135C is necessary to give the same fixing results as obtained at the 1-hour reading without lithium bromide or lithium p-toluene-sulfonate. The film containing piperidinium p-toluenesulfonate is heated for 30 minutes. The following table shows the extent of fixing difference of the different films:

N-methylolmethacrylamide is determined. Three solutions are formed, each having 0.374 gram of diphenylnitrone, 0.292 gram of M-methylolmethacrylamide, and 10 grams of 17 percent cellulose acetate in acetone. To produce Exarnple'XII, 0.020 gram of lithium bromide is added to one solution. As Example XIII,

PERCENT TRANSMISSION DATA FOR FILMS SHOWING EFFECT OF ADDED SALTS Icreent transmission Film area White Red Green Bide Salt added Example:

XII --LIIIIIIIIIII)I IIIIIIII --{i:::::::::: lji? $3 33322 llfi Percent difference 29. 20

XIII Lithium p-tolucnc-snlfomitc HE H Y Z E .l: cmo 211.2 70.80 14.50

Percent dilIcrence M 30.00 8.8 .2060 82.00

9 As shown in theabove table, the addition of the catalysts speeds the fixation of the nitrone image. The same results, substantially, are obtained as were obtained in the previous examples in one-fourth to one-half the heating time.

EXAMPLE XV The effect of different intensifiers is determined in this and following examples. A solution of 0.572 gram of diphenylnitrone, 0.383 gram of N,N-diphenyl-pphenylenediamine, and 0.500 gram of N-methylolmethacrylamide is prepared in grams of 17.3 percent cellulose acetate in acetone. The film is cast on Mylar producing a wet film of 7-mils thickness. The film is divided into four areas and exposed as in the immediately foregoing above'examples. Areas 3 and 4 are combined as area 4 and exposed 'for 15 minutes at cm distance from the 300-watt Gates Raymaster ultraviolet source. The exposed area 4 turns orange in color. The film is then heated at 135C. for 2 hours, causing the orange exposed areas to turn purple. Areas 2 and 4 are then exposed for 15 minutes. Area 1 remains unexposed. Optical density data are taken. The following table shows the results of the experiment:

Transmission Area White Red Green Blue 1 Unexposed 79.4 83.2 79.4 55.0 2. Exposed after heating 63.1 75.9 60.3 35.5 4. Exposed before heating 3.8 21.9 1.6 2.3 Difierence between 2 and 4 94.0 71.2 97.4 93.7 Change in maximum density due to intensifier (Compared with Example 111) 92.0 73.0 97.6 82.6

The addition of N,N'-diphenyl-p-phenylenediamine produces a startling reduction in the amount of light transmitted. The color produced is intensified greatly, as shown by data on area 4.

The same film can also be exposed through a Kodak 21 step tablet transparency to produce 11 steps of orange which become 11 steps of purple upon heating.

' EXAMPLE'XVI The N,Nf-diphenyl-p-phenylenediamine is replaced by p-methoxyphenol as an intensifier. A solution is prepared containing 0.434 gram of p-methoxyphenol in 10 ml. of 0.35 N solution of alpha,N-diphenylnitrone in acetone. This solution is spotted on three pieces of Whatman No. 2 filter paper. The first paper is exposed to a Gates Raymaster ultraviolet source for 15 minutes at 15 cm distance and then heated for 2 hours at 135C. The second paper is exposed but not heated. The third paper is heated but not exposed. A fourth paper is treated with 0.35 normal diphenylnitrone solution without added intensifier. This paper is exposed. The following table shows the results of the example.

The addition of p-methoxyphenol does not produce as great intensification as the addition of N,N'-

the intensifier as shown by the low percent reflections.

EXAMPLE XVII A solution of 0.98 gram of alpha,N-diphenylnitrone and 1.206 grams of N-methylolmethacrylamide is prepared in 100 ml. of methanol. The solution is spotted on Whatman No. 2 filter paper and dried. The paper is then exposed to an NBS line pattern by a Gates Raymaster ultraviolet lamp at a distance of 1 1 cm. The areas of the paper receiving light became brown while the unexposed areas remained white. The pattern is reproduced in sharp resolution. The paper is then heated at 110C. for 15 hours. Re-exposure of one-half of the paper to ultraviolet light under the same conditions as the first exposure results in no more than a slight yellowing of the background areas which were originally white. The contrast remains excellent. The experiment is repeated and the paper is heated to a temperature of 135C. instead of 110C. At this temperature, only 1 hour of heat treatment is required.

EXAMPLE XVIII A solution of 0.30 gram of alpha,N -diphenylnitrone and 0.233 gram of N-methylolmethacrylamide and 9.10 grams of 22.4 percent polystyrene in ethyl acetate is prepared. This solution is drawn on Mylar film to produce a film having a thickness of 7 mils wet The film is exposed to an image of ultraviolet light for 6 minutes at 17.5 cm distance. An excellentreproduction of the photographic negative is produced. A yellowbrown color is produced where light passed through the negative and the film is clear in other areas. The films are heated at 100C. for 24 hours. Re-exposure to the ultraviolet light does not cause noticeable darkening of the background or fading of the image when viewed under white light. The experiment is repeated and the film is heated for only 4 hours after exposure. Fixation is complete in this shorter time.

EXAMPLE XIX A solution of 0.879 gram of alpha,N-diphenylnitrone and 0.778 gram of N-methylolmethacrylamide is prepared in 16.30 grams of 24.3 percent cellulose acetate diphenyl-p-phenylene-diamine. However, the color is substantially darker than in .the experiments without in acetone. A film was cast from this solution. A portion of the surface of the film is exposed to ultraviolet light for 2 minutes at 11.5 cm distance while the remainder of the surface is covered. After heating the film sample at 135C. for 2 hours, a second portion of the film is exposed to ultraviolet light for 3 minutes with an area still unexposed. The optical densities of these three areas are shown in the following table:

Area White Light O.D. Blue Light O.D. Unexposed area 0.03 0.10 Exposed before heating 0.14 0.60 Exposed after heating 0.06 0.18

It will be noted that the area which is exposed before heating produced a dense image.

EXAMPLE XX The solution of 0.394 gram of alpha,N- diphenylnitrone and 0.1 54 gram of N,N

methylenebisacrylamide is prepared in 10 ml. of ethanol. The solution is spotted on three separate sheets of No. 2 Whatman filter paper identified as samples A, B and C. Samples B and C are placed immediately in a C. oven. Sample A- is kept at room temperature. After 1 hour, sample B is cooled to room temperature and exposed to ultraviolet light for 5 minutes at 20 cm distance. Sample A is also exposed to ultraviolet light lution is cast on Mylar producing l-mil dry thickness.

for 5 minutes at 20 cm distance. Sample C is exposed The film is exposed to a microfilm photographic negato ultraviolet light for 5 minutes at 20 cm distance after tive by a Gates Raymaster ultraviolet lamp for 20 minbeing heated for 24 hours at 100C. The optical densiutes at 17.5 cm distance. The resulting photographic tie of these spots are ho n in th follo i t bl 5 negative has excellent resolution. The clear areas of the negative produced a brown color in the copy.

Sample White Light CD. Blue Light 0D.

A 0.44 0.70 EXAMPLE XXV C 0.14 0.27 N-phenylacrylamide is incorporated into the solution of Example XXIV. The resulting film has good heat- It will be appreciated that the prolonged heating for. fixing properties.

24 hours results in a much less dense image.

EXAMPLE XXVI EXAMPLE XXI A solution of 2.04 grams of diphenylnitrone, 0.87 The effect of the addition of diphenylamine to digram of diphenylamine and 1.59 grams of N-methylolphenylnitrone on the maximum optical density of the methacrylarnide in 50 grams of 18.5 percent cellulose photochemical-reaction product of the mixture is deacetate is prepared. A film is cast on Mylar from the sotermined in this example. lution to a thickness of l-mil dry. The films are exposed The molar proportions of nitrone to amine ranged to a photographic negative by ultraviolet light from a from to 1 to 0.63 to l in gradual increments. A se- 20 Gates Raymaster lamp for 7% minutes at 20 cm disries of solutions is formed by adding diphenylamine to tance. The films are heated at 135C for 2 hours. Excela 0.350 molar solution of alpha,N-diphenylnitrone in lent contact print copies of the negative are produced.

ethanol. Each solution was spotted on filter paper and exposed to ultraviolet radiation for 5 minutes at 20 cm EXAMPLES XXIX di t e aft d in An i blo er i d t k e th These examples show the effect of substituents such surface temperatures of the spots from exceeding C. as a methoxy (or nitro) group on the alpha-phenyl A plot of the percent reflections of these spots to white, group of alpha,N-diphenylnitrone. Solutions of a conred, green, and blue light versus the concentration of centration of 0.175 M, each of alpha-(pamine results in a smooth curve showing that the permethoxyphenyl)-N-phenylnitrone, alpha-(3,4- cent reflection decreases with added amine. A decrease 30 dimethoxyphenyl )-N-phenylnitrone, and of alpha,N- in percent reflection corresponds to an increase in optidiphenylnitrone, are coated on No. 2 filter paper.

cal density. The following table gives the data for the The samples are irradiated for 30 minutes. The unex- 20 to 1 solution and the 0.63 to 1 solution as well as for Posed SPOtS ye owhe Opti al densities of the exthe solution of nitrone alone. posed spots are shown on the following table.

Percent Reflection 1 White light Red light Green light Blue light Mole ratio nitrone: amine:

20=1 31.02 (24.15) 50.12 (24.14) 30. 20 (25.87) 18. 20 (16.82) 0.01m 10. 00 (60.18) 21. 88 (66.88) 15. 85 (01.34) 12.02 (45.06) Nitrone alone in 0.350 M solution 41. 69 6G. 07 40. 74 21. 88

1 Values in parentheses are the percent differences due to added amino.

EXAMPLE XXll COMPARISON OF OPTICAL DENSlTlES OF NlTRONE IMAGES The nitrones of the present invention may be used in E l R G l the process of photocopying on paper. A solution of 322; ed B 8.65 grams of alpha,N-diphenylnitrone, 7.40 grams of methoxyphenyD-N- diphenylamine and 8.10 grams of N,N- a] g i'g g methylenebisacrylamide is impregnated on a sheet of Yfimcflioxyphenyl)- paper. The paper is exposed to a photographic negative lf 033 047 by ultraviolet radiation from a Gates Raymaster lamp f gi g 0A1 Q23 0'42 062 for 1 minute at 15 cm distance. An excellent contact print is formed which has excellent resolution and tone The methoxy Substituent i not Provide a denser reproductlon' image than the unsubstituted nitrone.

EXAMPLE xx111 EXAMPLE XXX The effect on the intensity of the image of the addi- A sheet of paper impregnated as i E l XXII i tion of diphenylamine to a coating containing diphenylexposed in contact witb a photographic negative of a nitrone iS determinedprinted page. The print is reproduced in excellent resoph nylni r n iS diSSOlVed in B a I t0 8 00 10611- lution. it is fixed by heating at 135C. for 1 hour. Color t ation of 0350M. Diphenylamine is added to give a varied from chocolate brown through bluish brown to Concentration g g from 0-0175M t0 0560M, in a steel gray. series of solutions, and the solutions are spotted on filter paper, dried and irradiated. As the concentration of EXAMPLE XXIV diphenylamine increases, the percent reflection de- A solution of 0.20 gram of diphenylnitrone and 0,17 creases until equimolar proportions are reached, at

gram of diphenylamine in 17.2 grams of 29.1 percent which time the percent reflection changes less percepsolution of polystyrene in toluene is prepared. The sotibly(also see Example XXI).

It will be apparent that many changes and modifications of the several features described herein may be made without departing from the spirit and scope of the invention. It is therefore apparent that the foregoing description is by way of illustration of the invention rather than limitation of the invention.

What is claimed is:

1. Process for producing a visible image comprising:

exposing to actinic radiation at least a portion of a photo-sensitive medium carrying a photosensitive nitrone to convert said nitrone to a product giving increased optical densities in the exposedareas of said medium; said photosensitive nitrone having the formula RCH=N( O)R wherein R is selected from the group consisting of aryl including substituted phenyl, aroyl, arylvinylene and furyl groups and R is an aryl group including substituted phenyl, said substituted phenyl having one or two substituents selected from the group consisting of dimethylamino, hydroxy, methoxy, methyl and nitro; I and heat-treating said medium at a temperature of at least 100C for a period of time sufficient to convert said nitrone in unexposed image areas to a radiation-stable product of low optical density.

2. The process of claim 1, in which each of the R and R groups of the nitrone is selected from the group consisting of phenyl, naphthyl, and substituted phenyl.

3. The process of claim 1, in which each of the R and R groups of the nitrone is selected from the group consisting of phenyl and l-naphthyl.

4. Theprocess of claim 1, in which said photosensitive nitrone is alpha,N-diphenylnitrone.

5. The process ,of claim 1, in which said heat-treating is carried out at a temperature approximating 135C.

6. Process for producing a visible image comprising: exposing to actinic radiation at least a portion of a photo-sensitive medium carrying (l) a photosensitive nitrone having the formula RCH=N( O)R wherein R is selected from the group consisting of aryl including substituted phenyl, aroyl, arylvinylene and furyl groups and R is an aryl group including substituted phenyl, said substituted phenyl'having one or two substituents selected from the group consisting of dimethylamino, hydroxy, methoxy, methyl and nitro, and (2) an intensifier compound selected from the group consisting of diphenylamine, p-phenylenediamine, N,N'-diphenyl-pphenylenediamine, indole, 3-indolylacetic acid, carbazole, benzimidazole, rhodanine and p-methoxyphenol to convert said nitrone to a product giving increased optical densities in the exposed areas of said medium and heat-treating said medium at a temperature of at least 100C for a period of time sufficient to convert said nitrone in unexposed image areas to a radiationstable product of low optical density.

7. The process of claim 6, in which each of the R and R groups of the nitrone is selected from the group consisting'of phenyl and l-naphthyl.

8. The process of claim 7, in which the intensifier compound is N,N-diphenyl-p-phenylenediamine.

9. The process of claim 6, in which the intensifier compound is diphenylamine.

10. The process of claim 6, in which the intensifier compound is N,N-diphenyl-p-phenylenediamine.

11. The process of claim 6, in which the intensifier compound is p-methoxyphenol.

12. The process of claim 6, in which said photosensitive nitrone is alpha,N-diphenylnitrone and said intensifier is the compound N,N-diphenyl-pphenylenediamine.

13. Process for producing a visible image comprising: exposing to actinic radiation at least a portion of a photosensitive medium carrying (l) a photosensitive nitrone having the formula RCH=N( O)R wherein R is selected from the group consisting of aryl including substituted phenyl, aroyl, arylvinylene and furyl groups and R is an aryl group including substituted phenyl, said substituted phenyl having one or two substituents selected from the group consisting of dimethylamino, hydroxy, methoxy, methyl and nitro, and (2) a heatfixing catalyst selected from the group consisting of tricresyl phosphate, phosphorus trichloride, phosphorus pentachloride, sulfur dioxide, thionyl chloride, acetic anhydride and maleic anhydride to convert said nitrone to a product giving increased optical densities in the exposed image areas of said medium and heat-treating said medium at a temperature of at least C for a period of time sufficient to convert said nitrone in unexposed image areas to a radiationstable product of low optical density.

14. The process of claim 13, in which each of the R and R groups of the nitrone is selected from the group consisting of phenyl and l-naphthyl.

15. The process of claim 14, inwhich the heat-fixing catalyst is tricresyl phosphate.

16. The process of claim 13, in which the heat-fixing catalyst is tricresyl phosphate.

17. The process of claim 13, in which said photosensitive nitrone is alpha,N-diphenylnitrone and said heatfixing catalyst is tricresyl phosphate.

18. Process for producing a visible image comprising:

exposing to actinic radiation at least a portion of a photosensitive medium carrying (l) a photosensitive nitrone having the formula RCH=N(- O)R' wherein R is selected from the group consisting of aryl including substituted phenyl, aroyl, arylvinylene and furyl groups and R is an aryl group including substituted phenyl, said substituted phenyl having one or two substituents selected from the group consisting of dimethylamino, hydroxy, me-

thoxy, methyl and nitro, (2) an unsaturated compound selected from the group consisting of (a) the lower alkyl esters of acrylic acid, methylsubstituted acrylic acid and fumaric acid and the nitriles corresponding to said acids; (b) N- phenylamides, N-lower-alkylamides and N-lowerhydroxyalkyl amides of acrylic acid and methylsubstituted acrylic acid; (c) N-vinyl succinimide and N-vinyl phthalimide; (d) styrene and phenylacetylene and (e) 3-sulfolene and (3) reaction products of said nitrone and said unsaturated compound to convert said nitrone to a product giving increased optical densities in the exposed image areas of said medium and heat-treating said medium at a temperature of at least 100C for a period of time sufficient to convert said nitrone in unexposed image areas to a radiation-stable product of low optical density.

19. The process of claim 18, in which said unsaturatedcompound is selected from the group consisting of acrylonitrile, fumaronitrile, dimethyl fumarate, ac-

rylamide, N-phenylacrylamide, N,N'- methylenebisacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-vinylsuccinimide, N- vinylphthalimide, styrene, phenylacetylene, and 3- sulfolene.

20. The process of claim 19, in which said photosensitive medium carries additionally a salt selected from the group consisting of lithium bromide, lithium p-toluenesulfonate, and piperidinium p-toluenesulfonate for increasing the reactivity of said unsaturated compound during said heat-treating to provide a radiation-stable reaction product of unexposed nitrone and said unsaturated compound.

22. The process of claim 18, in which each of the R and R groups of the nitrone carried by said medium is selected from the group consisting of phenyl and 1- naphthyl, and in which said photosensitive medium carries N-methylolmethacrylamide for facilitating the production, during said heat-treating, of said low-optical-density radiation-stable product in unexposed image areas which includes a reaction product of the unexposed nitrone and the N-methylolmethacrylamide.

23. The process of claim 22, in which said photosensitive medium carries additionally piperidinium p-toluene-sulfonate for increasing the reactivity of the N-methylolmethacrylamide with the nitrone in unexposed image areas during said heat-treating.

24. The process of claim 22, in which said photosensitive medium carries additionally N,N'-diphenyl-pphenylenediamine for further increasing optical density responsive to said conversion of the nitrone in the exposed image areas.

25. The process of claim 22, in which said photosensitive medium carries additionally diphenylamine for further increasing optical density responsive to said conversion of the nitrone in the exposed image areas. 

2. The process of claim 1, in which each of the R and R'' groups of the nitrone is selected from the group consisting of phenyl, naphthyl, and substituted phenyl.
 3. The process of claim 1, in which each of the R and R'' groups of the nitrone is selected from the group consisting of phenyl and 1-naphthyl.
 4. The process of claim 1, in which said photosensitive nitrone is alpha,N-diphenylnitrone.
 5. The process of claim 1, in which said heat-treating is carried out at a temperature approximating 135*C.
 6. Process for producing a visible image comprising: exposing to actinic radiation at least a portion of a photo-sensitive medium carrying (1) a photosensitive nitrone having the formula RCH N( -> O)R'' wherein R is selected from the group consisting of aryl including substituted phenyl, aroyl, arylvinylene and furyl groups and R'' is an aryl group including substituted phenyl, said substituted phenyl having one or two substituents selected from the group consisting of dimethylamino, hydroxy, methoxy, methyl and nitro, and (2) an intensifier compound selected from the group consisting of diphenylamine, p-phenylenediamine, N,N''-diphenyl-p-phenylenediamine, indole, 3-indolylacetic acid, carbazole, benzimidazole, rhodanine and p-methoxyphenol to convert said nitrone to a product giving increased optical densities in the exposed areas of said medium and heat-treating said medium at a temperature of at least 100*C for a period of time sufficient to convert said nitrone in unexposed image areas to a radiation-stable product of low optical density.
 7. The process of claim 6, in which each of the R and R'' groups of the nitrone is selected from the group consisting of phenyl and 1-naphthyl.
 8. The process of claim 7, in which the intensifier compound is N,N''-diphenyl-p-phenylenediamine.
 9. The process of claim 6, in which the intensifier compound is diphenylamine.
 10. The process of claim 6, in which the intensifier compound is N,N''-diphenyl-p-phenylenediamine.
 11. The process of claim 6, in which the intensifier compound is p-methoxyphenol.
 12. The process of claim 6, in which said photosensitive nitrone is alpha,N-diphenylnitrone and said intensifier is the compound N,N''-diphenyl-p-phenylenediamine.
 13. Process for producing a visible image comprising: exposing to actinic radiation at least a portion of a photosensitive medium carrying (1) a photosensitive nitrone having the formula RCH N( -> O)R'' wherein R is selected from the group consisting of aryl including substituted phenyl, aroyl, arylvinylene and furyl groups and R'' is an aryl group including substituted phenyl, said substituted phenyl having one or two substituents selected from the group consisting of dimethylamino, hydroxy, methoxy, methyl and nitro, and (2) a heat-fixing catalyst selected from the group consisting of tricresyl phosphate, phosphorus trichloride, phosphorus pentachloride, sulfur dioxide, thionyl chloride, acetic anhydride and maleic anhydride to convert said nitrone to a product giving increased optical densities in the exposed image areas of said medium and heat-treating said medium at a temperature of at least 100*C for a period of time sufficient to convert said nitrone in unexposed image areas to a radiation-stable product of low optical density.
 14. The process of claim 13, in which each of the R and R'' groups of the nitrone is selected from the group consisting of phenyl and 1-naphthyl.
 15. The process of claim 14, in which the heat-fixing catalyst is tricresyl phosphate.
 16. The process of claim 13, in which the heat-fixing catalyst is tricresyl phosphate.
 17. The process of claim 13, in which said photosensitive nitrone is alpha,N-diphenylnitrone and said heat-fixing catalyst is tricresyl phosphate.
 18. Process for producing a visible image comprising: exposing to actinic radiation at least a portion of a photosensitive medium carrying (1) a photosensitive nitrone having the formula RCH N( -> O)R'' wherein R is selected from the group consisting of aryl including substituted phenyl, aroyl, arylvinylene and furyl groups and R'' is an aryl group including substituted phenyl, said substituted phenyl having one or two substituents selected from the group consisting of dimethylamino, hydroxy, methoxy, methyl and nitro, (2) an unsaturated compound selected from the group consisting of (a) the lower alkyl esters of acrylic acid, methyl-substituted acrylic acid and fumaric acid and the nitriles corresponding to said acids; (b) N-phenylamides, N-lower-alkylamides and N-lower-hydroxyalkyl amides of acrylic acid and methyl-substituted acrylic acid; (c) N-vinyl succinimide and N-vinyl phthalimide; (d) styrene and phenylacetylene and (e) 3-sulfolene and (3) reaction products of said nitrone and said unsaturated compound to convert said nitrone to a product giving increased optical densities in the exposed image areas of said medium and heat-treating said medium at a temperature of at least 100*C for a period of time sufficient to convert said nitrone in unexposed image areas to a radiation-stable product of low optical density.
 19. The process of claim 18, in which said unsaturated compound is selected from the group consisting of acrylonitrile, fumaronitrile, dimethyl fumarate, acrylamide, N-phenylacrylamide, N,N''-methylenebisacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-vinylsuccinimide, N-vinylphthalimide, styrene, phenylacetylene, and 3-sulfolene.
 20. The process of claim 19, in which said photosensitive medium carries additionally a salt selected from the group consisting of lithium bromide, lithium p-toluenesulfonate, and piperidinium p-toluenesulfonate for increasing the reactivity of said unsaturated compound during said heat-treating to provide a radiation-stable reaction product of unexposed nitrone and said unsaturated compound.
 21. The process of claim 19, in which said photosensitive medium carries additionally an intensifier, for further increasing optical density responsive to said conversion of the nitrone in the exposed image areas, in the form of a compound selected from the group consisting of diphenylamine, p-phenylenediamine, N,N''-diphenyl-p-phenylenediamine, indole, 3-indolylacetic acid, carbazole, benzimidazole, rhodanine, and p-methoxyphenol.
 22. The process of claim 18, in which each of the R and R'' groups of the nitrone carried by said medium is selected from the group consisting of phenyl and 1-naphthyl, and in which said photosensitive medium carries N-methylolmethacrylamide for facilitating the production, during said heat-treating, of said low-optical-density radiation-stable product in unexposed image areas which includes a reaction product of the unexposed nitrone and the N-methylolmethacrylamide.
 23. The process of claim 22, in which said photosensitive medium carries additionally piperidinium p-toluene-sulfonate for increasing the reactivity of the N-methylolmethacrylamide with the nitrone in unexposed image areas during said heat-treating.
 24. The process of claim 22, in which said photosensitive medium carries additionally N,N''-diphenyl-p-phenylenediamine for further increasing optical density responsive to said conversion of the nitrone in the exposed image areas.
 25. The process of claim 22, in which said photosensitive medium carries additionally diphenylamine for further increasing optical density responsive to said conversion of the nitrone in the exposed image areas. 